(1) Field of the Invention
This invention relates to and has as its principal object the provision of ways of overcoming a new type of deposit formation in gasoline and diesel engines by inclusion into the fuel composition a fuel-soluble complexing agent.
(2) Background Information
Original equipment manufactures of automotive vehicles have recently been experiencing a perplexing deposit problem, namely the formation of new types of deposits on injector system components of gasoline and diesel engines equipped with fuel injectors such as port fuel injectors, solenoid activated injectors, and the like. These deposits differ from the conventional type of deposits that tend to form both in carbureted fuel induction systems and in fuel injection systems of gasoline and diesel powered engines. The conventional deposits are gums or other organic residues that are believed to result primarily from the fuel itself or at least constituents thereof. Such deposits can be and have been effectively controlled by use of fuel additives that serve as detergents. A number of such additives are in widespread commercial use in present-day gasolines. Unfortunately, however, conventional detergent additives are ineffective in controlling these new types of deposits. These new types of deposits adhere tenaciously to fuel induction system components such as poppet valves of port fuel injectors, pintles of other types of fuel injection systems, intake valves, and the like. Such deposits can seriously interfere with proper engine operation.
These new types of deposits have been found to contain a substantial amount of inorganic material along with some organic binder materials. We have found for example that deposits formed on the intake valves of a 2.3 liter gasoline engine operated on an ordinary gasoline composition contained 5.1 wt % of sodium sulfate. Likewise we found that deposits that formed in a multiport fuel injector of a vehicle contained 2.1 wt % of sodium sulfate.
We have found that deposits formed on the fuel injectors of a diesel engine operated on an ordinary diesel fuel composition contained from 0.75 to 1.18 wt % of sodium sulfate. By Energy Dispersive X-ray Spectroscopy (lEDS), we have confirmed the presence of carbon, oxygen, zinc, magnesium, silicon, phosphorous, sulfur, calcium, chromium, iron, and the alkali metals sodium and potassium.
Without desiring to be bound by theoretical considerations, it is believed that these inorganic deposits result from the presence of trace quantities of inorganic salts in hydrocarbon fuels such as gasoline and diesel fuel which have been formed from hydrocarbon components (e.g., alkylates) prepared by processes in which acids or acidic materials such as sulfuric acid or hydrogen fluoride are neutralized with certain basic substances such as sodium hydroxide or potassium hydroxide. Such processing is believed to cause metal salts to be carried over into the finished fuel in trace amounts, perhaps in ionic form in trace amounts of water in the fuel. While in the past such salts may have been present in hydrocarbon fuels, their presence apparently caused no known problems. However their presence in fuels used in modem production and prototype engines equipped with fuel injection systems of modem design appears to have caused this new deposit problem. But whatever its precise cause, the new deposit problem can be traced to the presence in the fuel of trace amounts of alkali metal-containing impurities such as one or more alkali metal salts. Typically, the amounts of such impurities correspond to up to about 10 micrograms of alkali metal per milliliter of the fuel.